It is possible to support an object via a four-joint link mechanism and to shift the object from a position A to a position B while operating the four-joint link mechanism by use of an electric motor. A seat for a vehicle, which is disclosed in JP2003-118451, is described as an example hereinafter.
A seat for a vehicle has a seat cushion and a foldable seat back. The seat cushion and the folded seat back are stowed in a stowing space, such as a receiving recess, defined on a surface of a floor of a vehicle. The stowing space can be provided ahead of, or behind, the seat. Accordingly, it is possible to expand an inner space of a vehicle, to assure a space for placing baggage therein, and to allow an occupant to have an extra room to be seated in the vehicle so that the occupant can be relaxed for example.
A seat such as the seat for a vehicle described above, in which the seat can be stowed or retracted, includes a pair of front legs, which is freely pivotably supported at or about a front portion of a seat cushion frame, and a pair of rear legs, which is freely pivotably supported at or about a rear portion of the seat cushion frame. Each front and rear leg is normally engaged with a striker secured on a floor of a vehicle via a locking unit configured with a latch and a pawl, thereby keeping the seat at a use/deployed position at which an occupant can be seated on the seat cushion.
The front leg of the seat for a vehicle described above is connected to the rear leg by means of a lever. A shaft, which serves as a rotational axis of each rear leg, is operatively connected to the electric motor. Therefore, when the electric motor is driven, the shaft, i.e., the rotational axis of each rear leg, is rotated, and the rear leg can be pivoted in a rotational direction about the rotational axis. Meanwhile, the locking unit, which is configured with the latch and the pawl, is brought into an unlock state against the striker by an actuator.
As for the front leg, which is connected to the rear leg by means of the lever, the front leg is pivoted about a pivot via the lever which is moved in response to rotation of the rear leg. Meanwhile, the locking unit of the front leg, which is configured with the latch and the pawl, is brought into an unlock state against the striker by an actuator. In such circumstances, free ends of both front and rear legs approach each other. Both front and rear legs are folded, and the seat can be stowed at a predetermined position by a supporting member of the seat cushion.
The supporting member of the seat cushion is a four-joint link mechanism having a pair of first link and a pair of second link. One of the first links is arranged at a laterally one side of the seat, while the other one thereof is arranged at the laterally other side of the seat. One end of each first link is pivotably connected to the seat cushion, while the other end thereof is pivotably connected to the floor of the vehicle (in most cases, connected to a floor at both sides of a stowing space). Likewise, one of the second links is arranged at a laterally one side of the seat, while the other one thereof is arranged at the laterally other side of the seat. One end of each second link is operatively associated with the seat cushion, while the other end thereof is pivotably connected to the floor of the vehicle (in most cases, connected to a floor at both sides of a stowing space). The second link is pivotably supported by the seat cushion frame via the rear leg.
As described above, in response to rotation of the rear leg by the electric motor, the front leg is pivotably rotated via the lever, which connects the rear leg and the front leg, and one of the first link and the second link can be moved along a predetermined path so as to stow the seat at the predetermined position. Here, the other one of the first link and the second link is moved following the movements of the link moved along the predetermined path and the seat and expressing a fixed trajectory. Therefore, the seat of the vehicle is stowed inside a predetermined space in response to movements of the legs and the supporting member. Further, the seat of the vehicle can return or go back to the seat use/deployed position at which an occupant can be seated on the seat.
According to the above described seat, when an object (e.g., an occupant) is replaced or moved on the seat, or when the seat is switched between the stowed position and the use/deployed position, a degree of load applied to the electric motor may fluctuate in accordance with changes in a center of gravity of the object or the seat itself in a longitudinal direction or/and in a vertical direction. In such circumstances, an occupant may obtain an unpleasant feeling as to a smoothness of the seat movement, the smoothness which may become worse due to backlash of gears of a speed reducing mechanism of the electric motor. Moreover, the seat may be moved rapidly, to a position, at which the seat is expected to stop, or to a position, at which the locking unit establishes a locked state, which may supply an unpleasant feeling to an occupant.
The present invention has been made in view of the above circumstances, and provides a stowed-type or retracted-type seat which supplies a pleasant feeling to an occupant.